The invention is applicable to the field of antenna arrays. For a number of applications, a directional radiation pattern is desirable. By way of an example, a focused radiation in a preferred direction is required for detection and communication with a target. Avoiding electromagnetic pollution outside of the useful zones is another example of an application involving a relatively directional radiation pattern.
In order to increase the directivity of an antenna array, it is a known technique from the state of the art to use reflectors such as parabolic reflectors, to network antennas or to combine coupled antennas as in the case of antennas like the Yagi-Uda.
However, these solutions greatly increase the size of the antenna array. Indeed, the directivity of a reflector antenna is typically estimated by
  D  =                    4        ⁢                                  ⁢        π                    λ        2              ⁢    A  where A is the projected surface area visible along the main direction of radiation. In particular, this means that for a reflector disk of radius R,
  D  =                    4        ⁢                                  ⁢                  π          2                ⁢                  R          2                            λ        2              .  
It is also a known technique to jointly excite a mode of radiation such as the transverse electric (TE) type and a magnetic mode (TM) within a same given antenna array network. An antenna array structure that supports such an operation is called a Huygens source. For example, in the document FR-A-2949611, the teaching provides for a structure based on a resonator constituted of a ring shaped helical conductor that provides a Huygens source with a reduced antenna size.
However, the level of maximum directivity achievable with this type of antenna array structure is limited by the directivity of the ideal Huygens source, which is 4.7 dBi. The unit dBi signifies “decibel isotropic”. In a general sense, the directivity of an antenna is normally expressed in dBi, by taking as a reference an isotropic antenna, that is to say, a fictitious antenna of the same total radiated power that radiates uniformly in all directions with a radiation of 0 dBi.